audio - 如何使用 ffmpeg 从 Linux USB 捕获设备同时捕获音频和视频

Question

我正在通过 USB Terratec Grabster AV350(基于 em2860 芯片)捕获视频。

播放音频时我没有成功获取音频。如果我用 vlc 或 ffplay 播放捕获的视频，我只会听到 3 秒的声音，然后视频的其余部分一片寂静......

在捕获过程中我没有收到任何错误。最后它指示捕获的视频和音频的大小......

我为此使用 ffmpeg 命令:

ffmpeg -f alsa -ac 2 -i hw:3 -f video4linux2 -i/dev/video0 -acodec ac3 -ab 128k -vcodec mpeg4 -b 6000k -r 25 test5.avi

日志是:

[alsa @ 0x9bcd420]Estimating duration from bitrate, this may be inaccurate
Input #0, alsa, from 'hw:3':
Duration: N/A, start: 69930.998994, bitrate: N/A
Stream #0.0: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
[video4linux2 @ 0x9bf5d30]Estimating duration from bitrate, this may be inaccurate
Input #1, video4linux2, from '/dev/video0':
Duration: N/A, start: 1307111377.654173, bitrate: -2147483 kb/s
Stream #1.0: Video: rawvideo, yuyv422, 720x576, -2147483 kb/s, 1000k tbr, 1000k tbn, 1000k tbc
[ac3 @ 0x9bf9590]No channel layout specified. The encoder will guess the layout, but it might be incorrect.
Output #0, avi, to 'test5.avi':
Metadata:
ISFT : Lavf52.64.2
Stream #0.0: Video: mpeg4, yuv420p, 720x576, q=2-31, 6000 kb/s, 25 tbn, 25 tbc
Stream #0.1: Audio: ac3, 44100 Hz, stereo, s16, 128 kb/s
Stream mapping:
Stream #1.0 -> #0.0
Stream #0.0 -> #0.1
Press [q] to stop encoding
frame= 1283 fps= 25 q=2.3 Lsize= 38677kB time=51.32 bitrate=6173.9kbits/s
**video:37755kB audio:846kB** global headers:0kB muxing overhead 0.198922%

如果我减少只捕获音频的命令，那么音频文件就可以成功播放:

ffmpeg -f alsa -ac 2 -i hw:3,0 -acodec ac3 -ab 128k test5.avi

[alsa @ 0x8ede420]Estimating duration from bitrate, this may be inaccurate
Input #0, alsa, from 'hw:3,0':
Duration: N/A, start: 70395.998935, bitrate: N/A
Stream #0.0: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
[ac3 @ 0x8eebac0]No channel layout specified. The encoder will guess the layout, but it might be incorrect.
Output #0, avi, to 'test5.avi':
Metadata:
ISFT : Lavf52.64.2
Stream #0.0: Audio: ac3, 44100 Hz, stereo, s16, 128 kb/s
Stream mapping:
Stream #0.0 -> #0.0
Press [q] to stop encoding
size= 227kB time=13.62 bitrate= 136.8kbits/s
**video:0kB audio:213kB** global headers:0kB muxing overhead 6.902375%

如果我运行命令仅用于视频捕获，则 vlc 或 ffplay 可以成功播放视频:

ffmpeg -f video4linux2 -i/dev/video0 -vcodec mpeg4 -b 12000k -r 25 test5.avi

[video4linux2 @ 0x91d6420]Estimating duration from bitrate, this may be inaccurate
Input #0, video4linux2, from '/dev/video0':
Duration: N/A, start: 1307112044.025687, bitrate: -2147483 kb/s
Stream #0.0: Video: rawvideo, yuyv422, 720x576, -2147483 kb/s, 1000k tbr, 1000k tbn, 1000k tbc
Output #0, avi, to 'test5.avi':
Metadata:
ISFT : Lavf52.64.2
Stream #0.0: Video: mpeg4, yuv420p, 720x576, q=2-31, 12000 kb/s, 25 tbn, 25 tbc
Stream mapping:
Stream #0.0 -> #0.0
Press [q] to stop encoding
frame= 388 fps= 25 q=2.0 Lsize= 12963kB time=15.52 bitrate=6842.5kbits/s
**video:12949kB audio:0kB** global headers:0kB muxing overhead 0.114584%

我注意到的奇怪行为是，当我 try catch 视频和音频时，之后我无法再捕获音频， 除非我先拔掉AV350的插头。

G350 位于卡 3:

htpc@htpc-01:/proc/asound/G350/pcm0c$ more info
card: 3
device: 0
subdevice: 0
stream: CAPTURE
id: USB Audio
name: USB Audio
subname: subdevice #0
class: 0
subclass: 0
subdevices_count: 1
subdevices_avail: 1

操作系统是 Linux 2.6.38-8-generic，带有 Ubuntu Natty Narwhal 版本

任何关于如何解决这个问题的帮助都会很棒......

谢谢!

Answer 1

我正在做类似的事情，我使用了这个命令:

ffmpeg -y -f alsa -i default -f v4l2 -i /dev/video0 -acodec aac -strict -2 -ac 1 -b:a 64k -vcodec libx264 -b:v 300k -r 30 -g 30 prueba1.mp4

一开始我在使用 hw:3 组件时遇到了麻烦。相反，我输入了 default 并且代码实际上起作用了。我希望这会有所帮助。